High β phase content in PVDF/CoFe₂O₄ nanocomposites induced by DC magnetic fields Available to Purchase

Flexible ferroelectrics being exploited as energy harvesting and conversion materials are highly desirable for wearable and skin-mountable electronic devices. As one of the most typical ferroelectric polymers, poly(vinylidene fluoride) (PVDF) has been widely used in modern electronic systems and devices, whose ferroelectric performance relies heavily on its β phase content. In this work, to achieve high-β-phase-content PVDF, we first introduced CoFe₂O₄ nanoparticles into PVDF. With the incorporation of CoFe₂O₄ nanoparticles used as an effective polymer nucleation agent, the percentage of the β phase in the PVDF has been significantly enhanced, e.g., 84% in the nanocomposite with 5 wt. % CoFe₂O₄ versus only 73% in the pure PVDF. In order to further increase the β phase content in PVDF, we subsequently proposed an easily realized strategy. By applying DC magnetic fields during the solution-casting process of the PVDF/CoFe₂O₄ nanocomposites, a further improved β phase content as high as 95% can be achieved. The further improvement of the β phase content is attributable to the tensile stress at the CoFe₂O₄/PVDF interfaces created by the coupling of magnetic field and CoFe₂O₄ by means of the magnetostriction effect. The high β-phase content makes the PVDF/CoFe₂O₄ nanocomposites a promising candidate for flexible and wearable electronic device applications.